Substrate table, a lithographic apparatus and a device manufacturing method

ABSTRACT

A table for a lithographic apparatus, the table having a catchment opening formed in an upper surface of the table, the catchment opening in fluid communication through the table with the environment of the table at a drain opening in a surface of the table other than the upper surface.

This application is a continuation of U.S. patent application Ser. No.13/329,971, filed on Dec. 19, 2011, now allowed, which claims priorityand benefit under 35 U.S.C. §119(e) to U.S. Provisional PatentApplication No. 61/425,582, filed on Dec. 21, 2010. The contents ofthose applications are incorporated herein in its entirety by reference.

FIELD

The present invention relates to a table, a lithographic apparatus and amethod for manufacturing a device using a lithographic apparatus.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. In an embodiment, the liquid isdistilled water, although another liquid can be used. An embodiment ofthe invention will be described with reference to liquid. However,another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with higher refractive index thanair, desirably a higher refractive index than water. Fluids excludinggases are particularly desirable. The point of this is to enable imagingof smaller features since the exposure radiation will have a shorterwavelength in the liquid. (The effect of the liquid may also be regardedas increasing the effective numerical aperture (NA) of the system andalso increasing the depth of focus.) Other immersion liquids have beenproposed, including water with solid particles (e.g. quartz) suspendedtherein, or a liquid with a nano-particle suspension (e.g. particleswith a maximum dimension of up to 10 nm). The suspended particles may ormay not have a similar or the same refractive index as the liquid inwhich they are suspended. Other liquids which may be suitable include ahydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueoussolution.

Submersing the substrate or substrate and substrate table in a bath ofliquid (see, for example, U.S. Pat. No. 4,509,852) means that there is alarge body of liquid that must be accelerated during a scanningexposure. This requires additional or more powerful motors andturbulence in the liquid may lead to undesirable and unpredictableeffects.

In an immersion apparatus, immersion fluid is handled by a fluidhandling system, device structure or apparatus. In an embodiment thefluid handling system may supply immersion fluid and therefore be afluid supply system. In an embodiment the fluid handling system may atleast partly confine immersion fluid and thereby be a fluid confinementsystem. In an embodiment the fluid handling system may provide a barrierto immersion fluid and thereby be a barrier member, such as a fluidconfinement structure. In an embodiment the fluid handling system maycreate or use a flow of gas, for example to help in controlling the flowand/or the position of the immersion fluid. The flow of gas may form aseal to confine the immersion fluid so the fluid handling structure maybe referred to as a seal member; such a seal member may be a fluidconfinement structure. In an embodiment, immersion liquid is used as theimmersion fluid. In that case the fluid handling system may be a liquidhandling system. In reference to the aforementioned description,reference in this paragraph to a feature defined with respect to fluidmay be understood to include a feature defined with respect to liquid.

SUMMARY

If the immersion liquid is confined by a fluid handling system to alocalized area on the surface which is under the projection system, ameniscus extends between the fluid handling system and the surface. Ifthe meniscus collides with a droplet on the surface, this may result ininclusion of a bubble in the immersion liquid. The droplet may bepresent on the surface for various reasons, including because of leakagefrom the fluid handling system. A bubble in immersion liquid can lead toimaging errors, for example by interfering with a projection beam duringimaging of the substrate.

One way in which a bubble may be formed is that when the meniscus movesover the edge of the substrate W or other object, gas can get entrappedin the body of liquid, thereby forming a bubble. The gas that forms thebubble may come from the gap between the edge of the substrate W orother object and the section of the table surrounding the substrate W orother object. In order to help prevent bubbles from forming in this way,the table may comprise a two-phase extractor. The two-phase extractorinvolves drawing gas and, if present, liquid, down through the gap.

It is desirable, for example, to provide a lithographic apparatus inwhich the likelihood of bubble inclusion is at least reduced.

According to an aspect, there is provided a table for a lithographicapparatus, the table comprising a catchment opening formed in an uppersurface of the table, the catchment opening in fluid communicationthrough the table with the environment of the table at a drain openingin a surface of the table other than the upper surface.

According to an aspect, there is provided a lithographic apparatuscomprising the table as described above.

According to an aspect, there is provided a device manufacturing method,comprising:

projecting a patterned beam of radiation through an immersion liquidconfined to a space between a final element of a projection system and asubstrate supported on a substrate table;

catching immersion liquid in a catchment opening formed in an uppersurface of a table, the catchment opening in fluid communication throughthe table with the environment of the table at a drain opening in asurface of the table other than the upper surface; and

extracting immersion liquid at the drain opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 7 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 8 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 9 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 10 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 11 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 12 depicts, in cross-section, a substrate table for use in alithographic projection apparatus;

FIG. 13 depicts, in cross-section, a substrate table for use in alithographic projection apparatus; and

FIG. 14 depicts, in cross-section, a substrate table for use in alithographic projection apparatus.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

an illumination system (illuminator) IL configured to condition aradiation beam B (e.g. UV radiation or DUV radiation);

a support structure (e.g. a mask table) MT constructed to support apatterning device (e.g. a mask) MA and connected to a first positionerPM configured to accurately position the patterning device MA inaccordance with certain parameters;

a support table, e.g. a sensor table to support one or more sensors or asubstrate table WT constructed to hold a substrate (e.g. a resist-coatedsubstrate) W, connected to a second positioner PW configured toaccurately position the surface of the table, for example of a substrateW, in accordance with certain parameters; and

a projection system (e.g. a refractive projection lens system) PSconfigured to project a pattern imparted to the radiation beam B bypatterning device MA onto a target portion C (e.g. comprising one ormore dies) of the substrate W.

The illumination system IL may include various types of opticalcomponents, such as refractive, reflective, magnetic, electromagnetic,electrostatic or other types of optical components, or any combinationthereof, for directing, shaping, or controlling radiation.

The support structure MT holds the patterning device MA. It holds thepatterning device MA in a manner that depends on the orientation of thepatterning device MA, the design of the lithographic apparatus, andother conditions, such as for example whether or not the patterningdevice MA is held in a vacuum environment. The support structure MT canuse mechanical, vacuum, electrostatic or other clamping techniques tohold the patterning device MA. The support structure MT may be a frameor a table, for example, which may be fixed or movable as required. Thesupport structure MT may ensure that the patterning device MA is at adesired position, for example with respect to the projection system PS.Any use of the terms “reticle” or “mask” herein may be consideredsynonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device MA may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask),

The lithographic apparatus may be of a type having two or more tables(or stage or support), e.g., two or more substrate tables or acombination of one or more substrate tables and one or more sensor ormeasurement tables. In such “multiple stage” machines the multipletables may be used in parallel, or preparatory steps may be carried outon one or more tables while one or more other tables are being used forexposure. The lithographic apparatus may have two or more patterningdevice tables (or stages or support) which may be used in parallel in asimilar manner to substrate, sensor and measurement tables.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source SO and the lithographic apparatus may beseparate entities, for example when the source SO is an excimer laser.In such cases, the source SO is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source SO may be an integral part of thelithographic apparatus, for example when the source SO is a mercurylamp. The source SO and the illuminator IL, together with the beamdelivery system BD if required, may be referred to as a radiationsystem.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator IL can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator IL may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section. Similar to the source SO, the illuminator IL may or maynot be considered to form part of the lithographic apparatus. Forexample, the illuminator IL may be an integral part of the lithographicapparatus or may be a separate entity from the lithographic apparatus.In the latter case, the lithographic apparatus may be configured toallow the illuminator IL to be mounted thereon. Optionally, theilluminator IL is detachable and may be separately provided (forexample, by the lithographic apparatus manufacturer or anothersupplier).

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device MA. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions C (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam B is projected onto a target portion C at one time (i.e.a single static exposure). The substrate table WT is then shifted in theX and/or Y direction so that a different target portion C can beexposed. In step mode, the maximum size of the exposure field limits thesize of the target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam Bis projected onto a target portion C (i.e. a single dynamic exposure).The velocity and direction of the substrate table WT relative to thesupport structure MT may be determined by the (de-)magnification andimage reversal characteristics of the projection system PS. In scanmode, the maximum size of the exposure field limits the width (in thenon-scanning direction) of the target portion C in a single dynamicexposure, whereas the length of the scanning motion determines theheight (in the scanning direction) of the target portion C.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications in manufacturing components with microscale, or evennanoscale, features, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc.

Arrangements for providing liquid between a final element of theprojection system PS and the substrate can be classed into three generalcategories. These are the bath type arrangement, the so-called localizedimmersion system and the all-wet immersion system. In a bath typearrangement substantially the whole of the substrate W and optionallypart of the substrate table WT is submersed in a bath of liquid.

A localized immersion system uses a liquid supply system in which liquidis only provided to a localized area of the substrate. The space filledby liquid is smaller in plan than the top surface of the substrate andthe area filled with liquid remains substantially stationary relative tothe projection system PS while the substrate W moves underneath thatarea. FIGS. 2-5 show different supply devices which can be used in sucha system. A sealing feature is present to seal liquid to the localizedarea. One way which has been proposed to arrange for this is disclosedin PCT patent application publication no. WO 99/49504.

In an all wet arrangement the liquid is unconfined. The whole topsurface of the substrate and all or part of the substrate table iscovered in immersion liquid. The depth of the liquid covering at leastthe substrate is small. The liquid may be a film, such as a thin film,of liquid on the substrate. Immersion liquid may be supplied to or inthe region of a projection system and a facing surface facing theprojection system (such a facing surface may be the surface of asubstrate and/or a substrate table). Any of the liquid supply devices ofFIGS. 2-5 can be used in such a system. However, a sealing feature isnot present, not activated, not as efficient as normal or otherwiseineffective to seal liquid to only the localized area.

As illustrated in FIGS. 2 and 3, liquid is supplied by at least oneinlet onto the substrate, preferably along the direction of movement ofthe substrate relative to the final element. Liquid is removed by atleast one outlet after having passed under the projection system. As thesubstrate is scanned beneath the element in a −X direction, liquid issupplied at the +X side of the element and taken up at the −X side. FIG.2 shows the arrangement schematically in which liquid is supplied viainlet and is taken up on the other side of the element by outlet whichis connected to a low pressure source. In the illustration of FIG. 2 theliquid is supplied along the direction of movement of the substraterelative to the final element, though this does not need to be the case.Various orientations and numbers of in- and out-lets positioned aroundthe final element are possible; one example is illustrated in FIG. 3 inwhich four sets of an inlet with an outlet on either side are providedin a regular pattern around the final element. Note that the directionof flow of the liquid is shown by arrows in FIGS. 2 and 3.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets oneither side of the projection system PS and is removed by a plurality ofdiscrete outlets arranged radially outwardly of the inlets. The inletscan be arranged in a plate with a hole in its centre and through whichthe projection beam is projected. Liquid is supplied by one groove inleton one side of the projection system PS and removed by a plurality ofdiscrete outlets on the other side of the projection system PS, causinga flow of a thin film of liquid between the projection system PS and thesubstrate W. The choice of which combination of inlet and outlets to usecan depend on the direction of movement of the substrate W (the othercombination of inlet and outlets being inactive). Note that thedirection of flow of fluid and of the substrate is shown by arrows inFIG. 4.

Another arrangement which has been proposed is to provide the liquidsupply system with a liquid confinement structure which extends along atleast a part of a boundary of the space between the final element of theprojection system and the substrate table. Such an arrangement isillustrated in FIG. 5.

FIG. 5 schematically depicts a localized liquid supply system or fluidhandling system with a liquid confinement structure 12, which extendsalong at least a part of a boundary of the space between the finalelement of the projection system and the substrate table WT or substrateW. (Please note that reference in the following text to surface of thesubstrate W also refers in addition or in the alternative to a surfaceof the substrate table, unless expressly stated otherwise.) The liquidconfinement structure 12 is substantially stationary relative to theprojection system in the XY plane though there may be some relativemovement in the Z direction (in the direction of the optical axis). Inan embodiment, a seal is formed between the liquid confinement structure12 and the surface of the substrate W and may be a contactless seal suchas a gas seal (such a system with a gas seal is disclosed in Europeanpatent application publication no. EP-A-1,420,298) or liquid seal.

The liquid confinement structure 12 at least partly contains liquid inthe space 11 between a final element of the projection system PS and thesubstrate W. A contactless seal 16 to the substrate W may be formedaround the image field of the projection system PS so that liquid isconfined within the space between the substrate W surface and the finalelement of the projection system PS. The space 11 is at least partlyformed by the liquid confinement structure 12 positioned below andsurrounding the final element of the projection system PS. Liquid isbrought into the space below the projection system PS and within theliquid confinement structure 12 by liquid inlet 13. The liquid may beremoved by liquid outlet 13. The liquid confinement structure 12 mayextend a little above the final element of the projection system. Theliquid level rises above the final element so that a buffer of liquid isprovided. In an embodiment, the liquid confinement structure 12 has aninner periphery that at the upper end closely conforms to the shape ofthe projection system or the final element thereof and may, e.g., beround. At the bottom, the inner periphery closely conforms to the shapeof the image field, e.g., rectangular, though this need not be the case.

The liquid may be contained in the space 11 by a gas seal 16 which,during use, is formed between the bottom of the barrier member 12 andthe surface of the substrate W. The gas seal is formed by gas. The gasin the gas seal is provided under pressure via inlet 15 to the gapbetween barrier member 12 and substrate W. The gas is extracted viaoutlet 14. The overpressure on the gas inlet 15, vacuum level on theoutlet 14 and geometry of the gap are arranged so that there is ahigh-velocity gas flow 16 inwardly that confines the liquid. The forceof the gas on the liquid between the barrier member 12 and the substrateW contains the liquid in a space 11. The inlets/outlets may be annulargrooves which surround the space 11. The annular grooves may becontinuous or discontinuous. The flow of gas 16 is effective to containthe liquid in the space 11. Such a system is disclosed in United Statespatent application publication no. US 2004-0207824, which is herebyincorporated by reference in its entirety. In an embodiment, the liquidconfinement structure 12 does not have a gas seal.

A control system 500 controls the overall operations of the lithographicapparatus and in particular performs an optimization process describedfurther below. Control system 500 may be embodied as asuitably-programmed general purpose computer comprising a centralprocessing unit, volatile and non-volatile storage means, one or moreinput and output devices such as a keyboard and/or a screen, one or morenetwork connections and one or more interfaces to the various parts ofthe lithographic apparatus. It will be appreciated that a one-to-onerelationship between controlling computer and lithographic apparatus isnot necessary. In an embodiment of the invention one computer maycontrol multiple lithographic apparatuses. In an embodiment of theinvention, multiple networked computers may be used to control onelithographic apparatus. The control system 500 may be configured tocontrol one or more associated process devices and substrate handlingdevices in a lithocell or cluster of which the lithographic apparatusforms a part. The control system 500 can also be configured to besubordinate to a supervisory control system of a lithocell or clusterand/or an overall control system of a fab.

FIG. 6 illustrates, in cross-section, a substrate table WT according toan embodiment of the invention. The substrate table WT comprises acatchment opening 61 formed in an upper surface 62 of the substratetable WT. The catchment opening (or fluid collection opening) 61 is influid communication through the substrate table WT with the environmentof the substrate table WT at a drain opening 63 in a surface 64 of thesubstrate table WT other than the upper surface 62. The environment ofthe substrate table WT is the immediate surroundings of the substratetable WT. The environment is the space immediately external to thesubstrate table WT. The undersurface 64 of the substrate table WT is indirect contact with the environment of the substrate table WT.

The catchment opening 61, the drain opening 63 and the flow path 65connecting the catchment opening 61 to the drain opening 63 may form atwo-phase extractor. A two-phase extractor extracts a mixture of liquidand gas. By having the catchment opening 61 in fluid communicationthrough the substrate table WT with the environment of the substratetable WT at the drain opening 63 a two-phase extractor that isbottomless is provided. This helps to reduce the thermal deformation ofcomponents of the lithographic apparatus. For example, one or moreencoder grid plates, which may comprise part of a positioning system toposition the substrate table WT, may be mounted on the substrate tableWT. U.S. patent application publication no. US 2007-0288121 describes anexemplary lithographic apparatus in which one or more encoder gridplates are on the upper surface 62 of the substrate table WT. One ormore encoder sensors may be fixed to a frame above the substrate tableWT. By providing a bottomless two-phase extractor, the encoder gridplates are less likely to be thermally deformed due to evaporativecooling. Such evaporated cooling results from the evaporation ofdroplets of liquid, e.g. immersion liquid, on the surface of thecomponent.

By forming the fluid communication between the catchment opening 61 andthe environment of the substrate table WT at the drain opening 63, nocables or hoses need to be connected to the substrate table WT forremoval of fluid from the catchment opening 61.

The catchment opening 61 may be used to catch gas and/or liquid from theupper surface of the substrate table assembly. The upper surface of thesubstrate table assembly may comprise an upper surface of one or moreselected from: the substrate W, a sensor, a sticker, a cover plate 103,the substrate table WT and other components of the lithographicapparatus positioned on the substrate table WT. A two-phase mixture ofgas and liquid may be caught by the catchment opening 61 into the flowpath 65. In an embodiment, only liquid is extracted from the flow path65 by the drain opening 63. In an embodiment the mixture of gas andliquid is extracted from the flow path 65 through the drain opening 63.The extraction through the drain opening 63 should be done in such a waythat substantially no liquid flows into any gaps between the uppersurface 62 of the substrate table WT and an undersurface of a component(e.g. cover plate 103) directly above the substrate table WT. In anembodiment, the catchment opening 61 is overhung by the upper surface ofthe substrate table assembly.

In an embodiment, the surface of the substrate table other than theupper surface is an undersurface 64 of the substrate table WT. Hence, inan embodiment, the drain opening 63 is in the undersurface 64 of thesubstrate table WT. The drain opening 63 is below the catchment opening61. This allows immersion liquid to be extracted from the upper surfaceof the substrate table assembly through the catchment opening 61 and thedrain opening 63 using gravity only. In this way, it is not necessary toprovide an active extractor. Hence, this system may be termed a passivetwo-phase extractor.

As depicted in FIG. 6, the substrate table WT may comprise a porousstructure 66 in a flow path 65 between the catchment opening 61 and adrain opening 63. The porous structure 66 may comprise a capillarystructure. The porous structure 66 may comprise a sieve, or amicrosieve. The porous structure 66 is desirably lyophilic. The purposeof the porous structure 66 is to maintain the level of liquid in theflow path 65. In this way, the amount of liquid which falls on theporous structure 66 is directly drained from the drain opening 63. As aresult, the volume of liquid in the flow path 65 stays approximatelyconstant.

In an embodiment, the drain opening 63 is in a side surface of thesubstrate table WT. The drain opening 63 can be in any surface of thesubstrate table WT provided that the drain opening is positioneddirectly or indirectly below the catchment opening 61. This allowsliquid in the catchment opening 61 to be extracted from the drainopening 63 by only gravity.

The porous structure 66 may comprise a porous medium. A porous mediummay be more robust than a microsieve. However, a microsieve has anadvantage over the porous medium in that the holes are better defined.

In an embodiment, an upper surface of the porous structure 66 is atleast 2 mm below the upper surface 62 of the substrate table WT. In anembodiment, the distance between the upper surface of the porousstructure 66 and the upper surface 62 of the substrate table WT is atleast 3 mm, at least 4 mm or at least 5 mm. A purpose of the minimumdistance of the depth of the flow path above the porous structure 66 isto help prevent immersion liquid from bridging between the fluidhandling structure 12 and the porous structure 66. Such bridginginvolves a continuous body of liquid between the fluid handlingstructure 12 and the porous structure 66. The liquid confined by thefluid handling structure 12 can form a bridge to the porous structure66, which may be lyophilic. If such bridging occurs, then this mayresult in draining the immersion liquid away from the fluid handlingstructure 12.

A further reason for the minimum distance is to help prevent bridgingbetween the undersurface of the substrate W and the porous structure 66.Such bridging may otherwise lead to liquid entering the gap between theundersurface of the substrate W and the substrate table WT.

When a droplet of liquid lands on the porous structure 66 in the flowpath 65, the droplet of liquid will pass through the holes of the porousstructure 66 and add to the volume of liquid below the porous structure66. The resulting reservoir of liquid below the porous structure 66drains to the drain opening 63 of the substrate table WT.

In an embodiment, the average radius of the pores in the porousstructure 66 is in the range of from about 10 micrometers to 100micrometers. The maximum radius of the pores may be larger, being of theorder of 100 s micrometers.

Liquid in the flow path 65, such as liquid stored in the porousstructure 66, may be lost through evaporation. In order to maintain thelevel of liquid in the flow path 65, the substrate table WT may comprisea liquid supply opening 67 in the flow path 65 below the porousstructure 66. The liquid supply opening 67 is configured to supplyliquid to the flow path 65. Hence, there is a passive drip feed ofliquid into the reservoir of liquid below the porous structure 66 inorder to keep the reservoir below the porous structure 66 substantiallyfull of liquid. The rate of evaporation of liquid from the flow path 65is likely to be relatively low. Therefore, it may be necessary for onlya few drops of liquid to be supplied to the flow path 65 from the liquidsupply opening 67 per cycle of exposure of a substrate W. The supply ofliquid through the liquid supply opening 67 can be used during startupof the lithographic apparatus in order to fill the reservoir below theporous structure 66.

The supply of liquid through the liquid supply opening 67 could beprovided during a substrate swap operation. In an embodiment, the liquidis re-supplied from a reference frame (not shown) when the substratetable WT docks with the reference frame during a table swap operation.

The lithographic apparatus may comprise a controller 500 (depicted inFIG. 1) configured to control a supply of liquid to the flow path 65between the catchment opening 61 and the drain opening 63 such thatliquid is supplied to the flow path 65 during at least one selectedfrom: startup of a lithographic apparatus, a substrate swap operationand/or a docking operation of the substrate table WT to a referenceframe of the lithographic apparatus.

The substrate table WT may comprise a liquid level sensor (not shown)configured to monitor the level of liquid in the flow path 65. Theliquid level sensor may be connected to the controller 500 to providethe controller with information regarding the level of liquid in theflow path 65. The controller 500 may be configured to control the supplyof liquid to the flow path 65 based on the output of the liquid levelsensor. In this way, the controller 500 can maintain the level of liquidin the flow path 65.

As depicted in FIG. 6, the catchment opening 61 may be in fluidcommunication with the environment at the drain opening 63 via at leastone capillary tube 68 extending to the drain opening 63. In theembodiment depicted in FIG. 6, the capillary tube 68 extends from thebottom of the reservoir below the porous structure 66 to the drainopening 63. The reservoir of liquid below the porous structure 66 candrain to the bottom of the substrate table WT via the capillary tube 68.In an embodiment, the substrate table WT comprises a series of capillarytubes 68.

FIGS. 9 and 10 depict embodiments in which a capillary tube 68 is notpresent. In the embodiments depicted in FIGS. 9 and 10, the two-phaseextractor is open-ended, with no narrowing of the structure from thecatchment opening 61 to the drain opening 63.

In FIG. 6, the reference letter h is used to refer to the distancebetween the lower surface of the porous structure 66 and the drainopening 63. The distance h is the vertical distance between these twopoints. In an embodiment, the distance h representing the height of thecolumn of liquid maintained in the flow path 65 is related to a maximumradius of pores of the porous structure 66 by the following equation:

${{\rho\;{gh}} = {\frac{2 \cdot \sigma}{r}\cos\;\theta}},$

where ρ is the density of immersion liquid, σ is the surface tension ofthe immersion liquid, r is the maximum radius of pores in the porousstructure 66, g is gravity, and θ is the contact angle of the immersionliquid with the porous structure 66.

The capillary tube 68 may have a width within the range of from about0.2 mm to about 2 mm, desirably within the range of from about 0.5 mm toabout 1 mm. As depicted in FIG. 6, a section of the surface 64 of thesubstrate table WT adjacent the drain opening 63 may be coated with alyophobic coating 69. As depicted in FIG. 6, the lyophobic coating 69may substantially surround the drain opening 63. The lyophobic coating69 may be adjacent the drain opening 63 in the undersurface 64 of thesubstrate table WT. The purpose of the lyophobic coating 69 is to helpprevent the undersurface 64 (or other surface in which the drain opening63 is positioned) from being wetted by the immersion liquid that isextracted from the drain opening 63. In an embodiment, the lyophobiccoating 69 is formed on only one side of the drain opening 63.

As depicted in FIG. 6, the drain opening 63 may be in the undersurface64 of the substrate table WT directly vertically below the catchmentopening 61. This allows the liquid caught in the catchment opening 61 toflow directly to the drain opening 63 from which it can be extracted.

In an embodiment, the porous structure 66 may substantially fill theflow path 65. In an embodiment, the porous structure may substantiallyfill the section of the flow path from the catchment opening 61 to thetop of the capillary tube 68. In this case, the function of the liquidsupply opening 67 in the flow path 65 is performed by the porousstructure 66. The porous structure 66 may be comprised of capillarymaterial. In this case, the system can be dried out. The first dropletsof liquid on the top surface of the porous structure 66 will fill up theporous structure 66 before draining starts.

However, it is possible that a porous structure 66 may becomecontaminated over time. This can lead to clogging of a porous structure,thereby resulting in a material that is gradually more lyophobic. Theporous structure 66 should therefore be cleaned periodically. In anembodiment, the porous structure 66 is detachable from the substratetable WT such that the porous structure 66 can be cleaned while thelithographic apparatus is offline.

In an embodiment, the porous structure 66 is coated in a glass material.A benefit of having a coating of glass material is that the coating ofglass material makes the porous structure 66 easier to clean. The glasscoating may also improve the lyophobicity of the porous structure 66.

The substrate table WT described above may be comprised in alithographic apparatus. The lithographic apparatus may further comprisea drip tray 70 below the substrate table WT. The drip tray 70 catchesliquid from the drain opening 63. The drip tray 70 is desirablypositioned directly vertically below the drain opening 63. The drip tray70 may be attached to the undersurface 64 of the substrate table WT. Thepurpose of this is that the drip tray 70 moves automatically along withthe substrate table WT such that the relative positions of the drip tray70 and the drain opening 63 is maintained. In an embodiment, the driptray 70 is attached to a long-stroke module 105 below the substratetable WT. The long stroke module moves the substrate table WT.

The lithographic apparatus may further comprise an active extractorconfigured to extract liquid from the drain opening 63. The activeextractor may comprise an underpressure generator 102 configured togenerate an underpressure in the environment of the drain opening 63.The active extractor may be comprised in a long-stroke module 105 belowthe substrate table WT. The active extractor removes the liquid from thesubstrate table WT.

The underpressure generator 102 may be attached to the long-strokemodule 105. The underpressure generator 102 may generate a partialvacuum in a region between the substrate table WT and the long-strokegenerator 102.

The catchment opening 61 may be positioned radially outward of asubstrate W supported on the substrate table WT. A cover plate 103 maybe positioned on an upper surface of the substrate table WT radiallyoutward of the substrate W. The catchment opening 61 may be positionedbetween the substrate W and the cover plate 103.

FIG. 7 depicts, in cross-section, a substrate table WT according to anembodiment of the invention. Components of the substrate table WTdepicted in FIG. 7 that are common to the substrate table WT depicted inFIG. 6 are given the same reference numerals. These components may eachhave the same features described above in relation to the correspondingcomponents depicted in FIG. 6.

As depicted in FIG. 7, the drain opening 63 may be offset from thecatchment opening 61. As a result, the drain opening 63 is not directlyvertically below the catchment opening 61. This is because the liquid inthe two-phase extractor does not have to be drained directly below thecatchment opening 61. A benefit of this arrangement is that lateralmovement of the substrate table WT (e.g. during a scanning operation)drains liquid from the flow path 65 of the two-phase extractor throughthe drain opening 63. Hence, both the lateral movement of the substratetable WT and gravity drain liquid from the two-phase extractor.

In the embodiment depicted in FIG. 7, acceleration of the substratetable WT in the horizontal plane (i.e. in the X-direction or in theY-direction) may lead to liquid draining through the flow path 65 andfrom the drain opening 63 away from the substrate table WT. As depictedin FIG. 7, the flow path 65 may take the form of a step with ahorizontal section between two vertical sections. In an embodiment, theflow path 65 may comprise a diagonal section extending downwards andradially outwards. The section of the flow path 65 that produces theoffset of the drain opening 63 from the catchment opening 61 may becomprised of a capillary tube 68.

In an embodiment, the drain opening 63 may comprise a rim 71 thatprotrudes from the surface 64 of the substrate table WT other than theupper surface 62. As depicted in FIG. 7, the rim 71 may be coated with alyophobic coating 72. The purpose of the lyophobic coating 72 and therim 71 is to help prevent the surface 64 of the substrate table WT inwhich the drain opening 63 is positioned from getting wet. The rim 71may perform this function either in addition to, or as an alternativeto, the lyophobic coating 69 as depicted in FIG. 6.

The embodiment depicted in FIG. 7 may comprise the drip tray 70described above in relation to the embodiment depicted in FIG. 6. Theembodiment depicted in FIG. 7 may comprise the underpressure generator102 described above in relation to the embodiment depicted in FIG. 6.The underpressure generator may be provided on a long-stroke module 105.The long stroke module 105 may be positioned below the two-phaseextractor. The two-phase extractor is contactless with respect to thelong-stroke module 105.

FIG. 8 depicts, in cross-section, a substrate table WT according to anembodiment of the invention. Components of the substrate table WTdepicted in FIG. 8 that correspond to components depicted in FIG. 6 orFIG. 7 are not described in detail. These components are given the samereference numerals and they may have the same features as describedabove.

As depicted in FIG. 8, a section of the surface 64 of the substratetable WT other than the upper surface 62 at only one side of the drainopening 63 may be coated with a lyophilic coating 81. The purpose of thelyophilic coating 81 is to transport the liquid from the drain opening63 away from a position directly under the two-phase extractor. By useof the lyophilic coating 81, the liquid from the drain opening 63 mayfollow the lyophilic coating 81 and subsequently drip where it meets alyophobic surface and/or a kink in the surface 64.

In an embodiment, a section of the surface 64 on the other side of thedrain opening 63 from the lyophilic coating 81 is coated with alyophobic coating 69. The lyophobic coating 69 may be radially inwardsof the drain opening 63. The lyophilic coating 81 may be radiallyoutwards of the drain opening 63.

In an embodiment, at the point where the drain opening 63 meets thelyophilic coating 81, the surface is smooth to help avoid pinning of theliquid. The surface at this point is desirably rounded, rather thanforming a sharp edge.

In an embodiment, the surface 64 radially outwards of the lyophiliccoating 81 is coated with a further lyophobic coating 82. The purpose ofthe further lyophobic coating 82 is to facilitate the liquid followingthe lyophilic coating 81 forming droplets that drip away from thesubstrate table WT. A drip tray 70 as described above may catch thedroplets.

In an embodiment, a section of the surface 64 of the substrate table WTin which the drain opening 63 is positioned slopes downwards away fromthe drain opening 63 at one side of the drain opening 63. As depicted inFIG. 8, the downward sloping section of the surface 64 may be thesection of the surface on which the lyophilic coating 81 is applied. Apurpose of the downward slope is to encourage the draining of liquidaway from the drain opening 63 along the lyophilic coating 81 towardsthe point at which it can drip away from the substrate table WT.

An advantage of this arrangement is that no external tubes may need tobe attached to the substrate table WT to extract fluid from a gap at theouter edge of the substrate W. Furthermore, evaporative cooling ofcomponents of the lithographic apparatus may be reduced or minimizedbecause substantially only liquid is drawn through the two-phaseextractor without significant gas being drawn in. The minimization ofevaporative cooling is significant to, for example, a system in which anencoder grid plate and/or sensor is mounted on the upper surface 62 ofthe substrate table WT. Such an encoder grid plate may be made of quartzfor example.

FIG. 9 depicts, in cross-section, a substrate table WT according to anembodiment of the invention. As depicted in FIG. 9, the width of thedrain opening 63 may be greater than or equal to the width of thecatchment opening 61. Hence, the two-phase extractor is open-ended atthe bottom. The drain opening 63 is formed in the undersurface 64 of thesubstrate table WT. The substrate table WT depicted in FIG. 9 has anadvantage of having a simple construction. As depicted in FIG. 9, awidth of the flow path 65 between the catchment opening 61 and the drainopening 63 may be greater than the width of the catchment opening 61.

An inner surface of the flow path 65 may be coated with a lyophobiccoating 91. The lyophobic coating 91 may form a continuous lyophobiccoating with the lyophobic coating 69 that is formed surrounding thedrain opening 63.

The embodiment depicted in FIG. 9 may comprise the drip tray 70described above in relation to the embodiment depicted in FIG. 6. Theembodiment depicted in FIG. 9 may comprise the underpressure generator102 described above in relation to the embodiment depicted in FIG. 6.The underpressure generator may be provided on a long-stroke module 105.The long stroke module 105 may be positioned below the two-phaseextractor. The two-phase extractor is contactless with respect to thelong-stroke module 105.

FIG. 10 depicts, in cross-section, a substrate table WT according to anembodiment of the invention. As depicted in FIG. 10, the substrate tableWT may comprise a sponge-like material 101 in the flow path 65 above theporous structure 66. The purpose of the sponge-like material 101 on topof the porous structure 66 is to increase the flow resistance of liquidthat may accumulate at this point. This helps prevent the liquid fromsloshing, which would otherwise result in undesirable dynamical forces.In an embodiment, the sponge-like material 101 comprises a sponge. Thesponge-like material 101 may have a minimum pore size of greater thanabout 3 mm. In an embodiment, the sponge-like material 101 isnon-capillary. A benefit of non-capillary sponge-like material is thatthe resistance to liquid flow above the porous structure 66 isincreased. This reduces undesirable dynamical forces that may otherwiseinterfere with the movement of the substrate table WT.

As depicted in FIG. 10, the porous structure 66 may be positioned at thebottom end of the two-phase extractor. The porous structure 66 may bepositioned in the drain opening 63. The porous structure 66 accumulatesexcess liquid above it and drips the liquid away from the substratetable WT at a controlled rate. The amount of liquid stored in the porousstructure 66 determines the amount of liquid that is extracted throughthe porous structure 66. The extraction may be passive, i.e. by onlygravity. The level of liquid on top of the porous structure 66 maydetermine the draining rate.

In an embodiment, the side wall of the flow path 65 between thecatchment opening 61 and the drain opening 63 is substantially verticalfrom the upper surface 62 of the substrate table WT to the drain opening63 in the undersurface 64 of the substrate table WT. This provides asubstrate table WT of simple construction.

The embodiment depicted in FIG. 10 may comprise the drip tray 70described above in relation to the embodiment depicted in FIG. 6. Theembodiment depicted in FIG. 10 may comprise the underpressure generator102 described above in relation to the embodiment depicted in FIG. 6.The underpressure generator may be provided on a long-stroke module 105.The long stroke module 105 may be positioned below the two-phaseextractor. The two-phase extractor is contactless with respect to thelong-stroke module 105.

As will be appreciated, any of the above-described features can be usedwith any other feature and it is not only those combinations explicitlydescribed which are covered in this application. For example, thefeature of the wider gap in the flow path 65 and optionally thelyophobic coating 91 on the inner surface of the flow path 65 depictedin FIG. 9 may be applied to any of the embodiments depicted in FIG. 6 to8 or 10. Such embodiments are depicted in FIGS. 11 to 14.

FIG. 11 depicts an embodiment in which the wider gap and optionallylyophobic coating 91 depicted in FIG. 9 are applied to the embodimentdepicted in FIG. 6. FIGS. 12, 13 and 14 correspond to embodiments of theinvention in which the wider gap and optionally the lyophobic coating 91depicted in FIG. 9 are applied to the embodiments depicted in FIGS. 7, 8and 10 respectively.

The embodiments depicted in FIGS. 11-14 may comprise the drip tray 70described above in relation to the embodiment depicted in FIG. 6. Theembodiments depicted in FIGS. 11-14 may comprise the underpressuregenerator 102 described above in relation to the embodiment depicted inFIG. 6. The underpressure generator may be provided on a long-strokemodule 10. The long stroke module 105 may be positioned below thetwo-phase extractor. The two-phase extractor is contactless with respectto the long-stroke module 105.

While the description herein has described embodiments in respect of asubstrate table, an embodiment of the invention may be applied to anytable. For example, in addition to or alternatively from a substratetable, an embodiment of the invention may be applied to a measurementtable having one or more sensors but not necessarily arranged to hold asubstrate.

In an embodiment, there is provide a table for a lithographic apparatus,the table comprising a catchment opening formed in an upper surface ofthe table, the catchment opening in fluid communication through thetable with the environment of the table at a drain opening in a surfaceof the table other than the upper surface.

In an embodiment, the surface of the table other than the upper surfaceis an undersurface of the table. In an embodiment, the table furthercomprises a porous structure in a flow path between the catchmentopening and the drain opening. In an embodiment, the maximum radius ofthe pores in the porous structure is in the range of from about 10 μm to100 μm. In an embodiment, the table further comprises a liquid supplyopening, in the flow path below the porous structure, to supply liquidto the flow path. In an embodiment, the table further comprises asponge-like material in the flow path above the porous structure. In anembodiment, the average pore size of the sponge-like material is greaterthan about 3 mm. In an embodiment, the porous structure substantiallyfills the flow path. In an embodiment, the catchment opening is in fluidcommunication with the environment at the drain opening via a capillarytube extending to the drain opening. In an embodiment, the averageradius of the capillary tube is in the range of from about 0.2 mm toabout 2 mm or in the range of from about 0.5 mm to about 1 mm. In anembodiment, the width of the drain opening is greater than or equal tothe width of the catchment opening. In an embodiment, a side wall of aflow path between the catchment opening and the drain opening issubstantially vertical from the upper surface of the table to the drainopening in an undersurface of the table. In an embodiment, a section ofthe surface of the table other than the upper surface adjacent the drainopening is coated with a lyophobic coating. In an embodiment, the drainopening is in an undersurface of the table directly vertically below thecatchment opening. In an embodiment, the drain opening is offset fromthe catchment opening. In an embodiment, the drain opening comprises arim that protrudes from the surface of the table other than the uppersurface. In an embodiment, the rim is coated with a lyophobic coating.In an embodiment, a section of the surface of the table other than theupper surface at only one side of the drain opening is coated with alyophilic coating. In an embodiment, a section of the surface of thetable other than the upper surface at one side of the drain openingslopes downwards away from the drain opening. In an embodiment, a widthof a flow path between the catchment opening and the drain opening isgreater than a width of the catchment opening. In an embodiment, thecatchment opening is radially outward of a substrate supporting area onwhich a substrate is to be supported.

In an embodiment, there is provided a lithographic apparatus comprisingthe table as described herein. In an embodiment, the lithographicapparatus further comprises a controller configured to control a supplyof liquid to a flow path between the catchment opening and the drainopening such that liquid is supplied to the flow path during at leastone selected from: startup of the lithographic apparatus, a substrateswap operation and/or a docking operation of the table to a referenceframe of the lithographic apparatus. In an embodiment, the lithographicapparatus further comprises a drip tray, below the table, to catchliquid from the drain opening. In an embodiment, the lithographicapparatus further comprises an active extractor configured to extractliquid from the drain opening. In an embodiment, the active extractorcomprises an underpressure generator configured to generate anunderpressure in the environment of the drain opening. In an embodiment,the lithographic apparatus further comprises a long-stroke module, belowthe table, to position the table, the long-stroke module comprising theactive extractor.

In an embodiment, there is provided a device manufacturing method,comprising: projecting a patterned beam of radiation through animmersion liquid confined to a space between a projection system and asubstrate supported on a substrate table; catching immersion liquid in acatchment opening formed in an upper surface of a table, the catchmentopening in fluid communication through the table with the environment ofthe table at a drain opening in a surface of the table other than theupper surface; and extracting immersion liquid at the drain opening.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm). The term“lens”, where the context allows, may refer to any one or combination ofvarious types of optical components, including refractive and reflectiveoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine-readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

Any controllers described herein may each or in combination be operablewhen the one or more computer programs are read by one or more computerprocessors located within at least one component of the lithographicapparatus. The controllers may each or in combination have any suitableconfiguration for receiving, processing, and sending signals. One ormore processors are configured to communicate with the at least one ofthe controllers. For example, each controller may include one or moreprocessors for executing the computer programs that includemachine-readable instructions for the methods described above. Thecontrollers may include data storage medium for storing such computerprograms, and/or hardware to receive such medium. So the controller(s)may operate according the machine-readable instructions of one or morecomputer programs.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath, only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion liquid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more fluid openingsincluding one or more liquid openings, one or more gas openings or oneor more openings for two-phase flow. The openings may each be an inletinto the immersion space (or an outlet from a fluid handling structure)or an outlet out of the immersion space (or an inlet into the fluidhandling structure). In an embodiment, a surface of the space may be aportion of the substrate and/or substrate table, or a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.The liquid supply system may optionally further include one or moreelements to control the position, quantity, quality, shape, flow rate orany other features of the liquid.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

The invention claimed is:
 1. A table for a lithographic apparatus, thetable comprising: a catchment opening formed in an upper surface of thetable, the catchment opening in fluid communication through the tablewith a drain opening in a surface of the table other than the uppersurface; a first porous structure in a flow path between the catchmentopening and the drain opening, wherein at least part of the flow path iswider than the catchment opening; and a second, further porous structurein the flow path between the catchment opening and the drain opening,wherein the second porous structure is configured to stop liquid flowand accumulate liquid above the second porous structure.
 2. The table ofclaim 1, further comprising a chamber in the flow path, the chamberhaving the catchment opening at an upper end thereof and an outletopening at a lower end thereof, wherein at least part of the chamber iswider than the catchment opening and the outlet opening and the firstand second porous structures are located between the catchment openingand the outlet opening.
 3. The table of claim 1, wherein the catchmentopening is in fluid communication with the environment of the table atthe drain opening.
 4. The table of claim 1, wherein the flow pathfurther comprises a collector portion below the first porous structureand above a substantially vertical or horizontal portion of a channelarrangement fluidly connecting the first porous structure and the drainopening, the collector portion configured to collect immersion liquidand being wider than the substantially vertical or horizontal portion.5. The table of claim 1, wherein the catchment opening is radiallyoutward of a substrate supporting area on which a substrate is to besupported.
 6. The table of claim 1, wherein a surface extending aroundat least part of the flow path is liquidphobic.
 7. The table of claim 1,further comprising a channel arrangement fluidly connecting the firstporous structure and the drain opening, the channel arrangementcomprising a first substantially vertical portion located below thefirst porous structure, a substantially horizontally extending portionconnected to the first substantially vertical portion and located belowthe first substantially vertical portion, and a second substantiallyvertical portion extending downward from the substantially horizontallyextending portion.
 8. The table of claim 1, wherein a rim of the drainopening protrudes from the surface of the table other than the uppersurface.
 9. A lithographic apparatus, comprising: a projection systemconfigured to project a beam of radiation through a liquid onto asubstrate; and a table comprising a catchment opening formed in an uppersurface of the table, the catchment opening in fluid communicationthrough the table with a drain opening in a surface of the table otherthan the upper surface; a first porous structure in a flow path betweenthe catchment opening and the drain opening, wherein at least part ofthe flow path is wider than the catchment opening; and a second, furtherporous structure in the flow path between the catchment opening and thedrain opening, wherein the second porous structure is configured to stopliquid flow and accumulate liquid above the second porous structure. 10.The apparatus of claim 9, further comprising a chamber in the flow path,the chamber having the catchment opening at an upper end thereof and anoutlet opening at a lower end thereof, wherein at least part of thechamber is wider than the catchment opening and the outlet opening andthe first and second porous structures are located between the catchmentopening and the outlet opening.
 11. The apparatus of claim 9, furthercomprising a channel arrangement fluidly connecting the first porousstructure and the drain opening, the channel arrangement comprising afirst substantially vertical portion located below the first porousstructure, a substantially horizontally extending portion connected tothe first substantially vertical portion and located below the firstsubstantially vertical portion, and a second substantially verticalportion extending downward from the substantially horizontally extendingportion.
 12. The apparatus of claim 9, wherein the catchment opening isin fluid communication with the environment of the table at the drainopening.
 13. The apparatus of claim 9, wherein the flow path furthercomprises a collector portion below the first porous structure and abovea substantially vertical or horizontal portion of a channel arrangementfluidly connecting the first porous structure and the drain opening, thecollector portion configured to collect immersion liquid and being widerthan the substantially vertical or horizontal portion.
 14. The apparatusof claim 9, wherein the catchment opening is radially outward of asubstrate supporting area on which a substrate is to be supported. 15.The apparatus of claim 9, wherein a surface extending around at leastpart of the flow path is liquidphobic.
 16. A table for a lithographicapparatus, the table comprising: a support surface configured to supportan object; a catchment opening formed in an upper surface of the table,the upper surface located at or below the support surface and thecatchment opening in fluid communication through the table with a drainopening in a surface of the table other than the upper surface; achamber in a flow path between the catchment opening and the drainopening, the chamber configured to collect immersion liquid and thechamber having the catchment opening at an upper end thereof and anoutlet opening at a lower end thereof, wherein at least part of thechamber is wider than the catchment opening and the outlet opening; anda porous structure located in the flow path and below the catchmentopening, wherein the porous structure is configured to stop liquid flowand accumulate liquid above the porous structure.
 17. The table of claim16, comprising a further porous structure located in the flow path andbetween the catchment opening and the drain opening.
 18. The table ofclaim 16, wherein a surface extending around at least part of the flowpath is liquidphobic.
 19. The table of claim 16, wherein the catchmentopening is in fluid communication with the environment of the table atthe drain opening.
 20. The table of claim 16, further comprising achannel arrangement fluidly connecting the chamber and the drainopening, the channel arrangement comprising a first substantiallyvertical portion located below the chamber, a substantially horizontallyextending portion connected to the first substantially vertical portionand located below the first substantially vertical portion, and a secondsubstantially vertical portion extending downward from the substantiallyhorizontally extending portion.